Apparatus for heat treating wire



May 17, 1932, M. H. GERRY, 3D., ET Al. 1,858,398

APPARATUS FOR HEAT` TREATING WIRE Filed May 31. 1928 nyu Patented May17, 1932 f UNITED STATES PATENT :oFiFIcE" MARTIN H. GERRY, 3D, OF SANFRANCISCO, AND CLAUDE J'. BROOKS, 0F REDWOOD CITY, CALIFORNIA,ASSIG-NORS TO E. I-I. EDWARDS CO., OF SAN FRANCISCO, CALIFORNIA,

A CORPORATION OF CALIFORNIA APPARATUS FOR HEAT TREATING WIRE Applicationled May 31,

Our invention relates to the process of heat treating wire,` andparticularlyto the double lead process of hardening or patenting steelwire, and its broad purpose is to provide a method of heat treatmentwhich may be practiced with a maximum economy of fuel and heat treatingmaterial, and with a minimum loss of time due to shut-downs.

`An object of our invention is to provide a method of using the leadprocess of heat treatment which obviates the constantly recurringshut-downs for replacing the pans in which the lead is heated.

Another object of our invention is to pro vide a process which minimizesthe wastage of lead, both from direct oxidation and spillage.

Still another object of our invention is to provide a method of treating`wire which conserves fuel.

A further object of our invention is to provide a method of treatingwire which yields a wire of uniform high quality.

Other objects of our invention are to provide an apparatus suitable forpracticing the method of our invention, and one 'which is not Subj ectto former limitations as to size.

Our invention possesses other objects and valuable features, some of.whichwill be set forth in the'following descriptionof our inventionwhich is illustrated in the drawings forming part of `the specification.It is to be understood that we do not limit ourselves to the showingmade by the said description andV drawings, as we may adopt veryingforms of our inventionv within .the scope of the claims.

In heat treating Wire, and especially in the hardening or patenting ofsteel wire, it

. is essential thatthe temperatures to which the material is subjected,and its rates of heating` and cooling, beheld within narrow limits.

Experience has proved that one of the most satisfactory ways of doingthis is to pass the wire through baths of fused material which aremaintained at the required temperatures. The material used for the bathsmay be a salt, such as barium chloride, or a metal having a suitablemelting point and a low affinity for the wire. Lead is perhaps the mostsuit- 1928. Serial No. 281,680.

able and widely used of these materials, and in the double lead processthe wire is first drawn through a bath of leadwhich is maintainedv at atemperature of about 1600o F., and isthen quenched in a secondbath,maintained at about 925 F. The large lrnass and thermal capacity of thebaths prevents vslight momentary fluctuations of intensity in theheating flames from developing hard or soft spots in the wire.; and thebaths also exclude air from contact with the wire during most of theprocess, and thereby prevent oxidation.

The lead is ordinarily heated in covered cast iron pans, upon which theflames play y from beneath. Owing to the high temperature at which thepans must be maintained their oxidation yis'very rapid', the averagelife of 'such a pan being about a week.` By substituting cast chromesteel for the cast iron pans this period may be extended to an averageof about three weeks, but atthe end of this time the furnace must beshut down, the brickwork torn out, and the panreplaced, with a loss ofabout 48 hours in running time and of a considerable quantity of fuel.

Moreover, there is loss of lead by oxidation from the surface of thebath, andyshould the pan crack and leakage occur, the spilled leadoxidizes almost instantly and passes'olf with the flue gases. It is tothe suppression of these losses and inconveniences that our invention isdirected.

The drawings show a wire treating furnace embodying our invention andadapted to the practice of our method; Fig. 1 being a plan, andFigs. 2and 3 being sectional views.` The planes of section are indicated,respectively, by the vlines 2 2 of Figure l and 3 3 of Figure 2. j

In terms of broad inclusion, our invention comprises the use of atreating bath formed in a refractory hearth and in a substantiallyclosed chamber. The bathis heated by the application of a reducing flameabove its surface, means being provided to screen a portion of thissurface from the action of the flame. A reducing agent, such as carbon,in the form of coke or charcoal is also preferably floated on thesurface of the bath for the further prevention of oxidation; Guides,

loo

surface'and so destroy thehearth. The end conveniently integral with thescreening means, direct the wire into and out of the screened portion ofthe surface of the bath. In the preferred method of operation, aquenching bath is also used,placed as closely as possible to the heatingbath, andthe fuel is conserved both by making this bath of suchdimensions that the heat carried to it by the treated wire is suliicienttomaintain it at the proper quenching temperature, and by drawing thewire toward the treating bath through a preheating chamber forming theflue through which the combustion gases are eX-V hausted. Y

In terms of greater detail, a preferred form ofthe apparatus of ourinvention comprises aheating furnace which is supported upon the I beams6. A heavy iron pan 7 rests upon the I beams,l and in this pan, upon asand cushion 8, is built an inverted arch hearth 9 of firefbrick orother suitable refractory material.

The side walls 10 lof the furnace rest directly on the pan 7, the sandcushion lying between them. The arch must be as carefully constructedand keyed as though it were uninverted and loaded in the usual Way, asotherwise .the buoyancy of the bricks in `the eX- ceedingly dense leadbath 11 held by the hearth would immediately bring them to the walls 12and 13 are, like the'arch, separated from the pan 7 by the sand cushion.Each end Wall is Vcapped by a guide 14, over which the wire 15 which isto be treated bends as it enters or leaves the furnace. These may be ofiron or, preferably, of chrome steel.

Stresses due to the expansion of the hearth V are transmitted throughthe cushion to the pan, which is reinforced to support them bytransverse I beams 16held by tension rods 17.

Built over'the hearth is a combustion chamber comprising the side walls10an arched roof 18,l and front and rear end walls 19 and 21, all of arefractory material such as fire-brick. The end walls are not directlyover those of the hearth, but are slightly closer together, and betweenthese walls and the end walls of the hearth are openings 22 and 23 forpassing the wire. The front opening 22 is as narrow as is convenientlypossible. The rear opening23vpasses the discharge gases and is made ofadequate size for this purpose. Buckstays 24 give structural stabilityto the furnace.

The front wall of the furnace is provided with a portthrough which aburner 26 directs a ame above the upper surface of the bath. A portionof the surface at eachy end is screened from the fiame by the baiiies 27and 28, each of which extends below the surface to serve as a guide forthe wire. As in the case of the guides 14, chrome steel appears to bethe most satisfactory material for these baffles, altho other materialsmay beused.V

Doors 29 in the side wall give access to the interior of the furnace forinspection or manipulation. l n

The exhaust gases from the furnace are led through the opening 23through a preheating chamber 31, formed of masonry with steelreinforcements r32, whence the gases pass downward through the flue 33and so to a stack34; At the back of the p-reheatin chamber guide rollers36 and guide pins 37 are provided te direct the various lines of wirethrough the opening 38 into the chamber. In theltop of the chamber nearits front end is a manhole 41, beneath which is a wire separator `orguide which preferably comprises a plurality of triangular ribs 42 on aflat base 43.

In front of the heating furnace is the l quenching bath 44 which is heldin a pan 46 having sloping sides. The rear edge of the pan is placed asclose to the guide 14 as possible, to minimize the time of transition ofthe wire between the baths. A masonry. com-y bustion chamber 47 having acentral wall 48 supports the pan; and a burner 49 Vis provided on eachside of the wall to supply the necessary heat. A flue 50 leads from thecombustion chamber to the stack 34.

Above the pan vadjustable guides are provided for directing the wirethrough the bath. These are held by brackets 51, andeach conn prises apair of levers 52 secured to a shaft53 and ycarrying a roller 54 betweentheir lower ends. A gear sector 56 is xed to each end. of the shaft andmeshes with a pinion 57 on a second shaft 58 which may be rotated by thecrank 59. It is thus possible. to raise the rollers above the surface ofthe bath for threading the wire beneath them.

An oil line 61 feeds the burners 26 and 49 and passes through the flue33 for preheating the oil. Suitable valves 62 are of course pro,- videdfor controlling each burner.

In starting operation, the baths are brought to temperature by means ofthe burners. The manhole 41 is opened and the wire lines arearrangedbetween the ribs of the separators, and then each line, with aniron plate secured to its end, is thrust into the bath and under thebaffle 28, the plate floating to the top of the molten bath. Otherwires, similarly floated, are inserted under the guide 27 from the otherend of the furnace and the wiresfrom the two ends are secured togetherby workmen operating throughthe doors 29. The wires are then pulledthrough the bath and threaded under the guides of the quenching bath,and all is ready for operation. n

The burner 26 is adjusted to givel a flame which will maintain areducing atmosphere over thebath and in the preheating chamber and thusprevent oxidation of the bath and of the wire. A reducing agent,preferably car# bon in the: form of charcoal or coke, is floated on thesurface of the bath for the further pre-y vention of oxidation.

The usual form of winding mechanism is used to draw the wire smoothlyand uniformly through the preheating chamber and the successive baths.After the operation is started, the flames from the burners 49 may bereduced or even extinguished completely, the quenching bath beingmaintained at the proper temperature by the heat carried to it by thewire.

In a furnace such as the one described, shutdowns are practicallyeliminated. The circulation of air between the I beams 6 under thefurnace keeps the iron pan 7 suciently cool so that little if anydeterioration takes place, and rebuilding of the furnace for replacingthe cast pans of usual practice is'of course eliminated. The temperatureof the quenching bath is not sufficiently high to cause rapiddeterioration of the pan or oxidation o-f the lead.

We claim:

l. In a wire treating furnace, a hearth composed of refractory earthmaterial for containing a bath of molten lead, means restraining thehearth against flotation, means for applying flame on lthe bath, meansfor guiding a wire through the bath, and means for confining the flameto a central portion of the bath to avoid burning the'wire as it entersand leaves the bath.

2. In a wire treating furnace, a hearth comprising an inverted arch ofrefractory earth material, means for supporting the arch,

means for applying flame over the hearth,

means for confining the flame to a central portion of the hearth, andmeans for passing Wire into and out of the furnace externally to saidcentral portion.

3. In a wire treating furnace, a sub-stantially closed chamber, a hearthcomposed of refractory earth material in said chamber for holding atreating bath, means for applying a flame on said bath; means forguiding the wire into, through, and out of said bath; means forscreening the wire from the direct action of the flame prior to itsentrance. into the bath, means for screening the wire from the directaction of the flame when it leaves said bath; a flue associated withsaid chamber, and means for guiding the wire through a p0rtion of saidflue prior to its entrance into the bath to effect preheating.

4. In a wire treating furnace, a substantially closed chamber, a'hearthcomposed of refractory earth material in said chamber for holding atreating bath, means for applying a flame on said bath; baffles adjacentoposed ends of the chamber for guiding the Wire into and through saidbath, and for screening the wire from the direct action of the flameprior to its entrance into, and when it leaves said bath; a flueassociated with said chamber, and means for guiding the wire through aportion of said flue prior to its entrance into the bath to effectpre-heating.

5. In a wire treating furnace a hearth of refractory material forcontaining a bath of molten lead through which the wire may be drawn,said hearth comprising a plurality of bricks laid to form an invertedarch, means for directing the wire into said bath, means In testimonywhereof, we have hereunto set i our hands.

MARTIN H. GERRY, 3RD.

CLAUDE J. BROOKS.

